In a plasma processing apparatus used for an etching step or a film formation step in the semiconductor manufacturing process, the electrodes to which high frequency voltage is applied to generate plasma in a plasma generation container are an important component. For example, in a typical plasma processing apparatus of a type provided with parallel flat electrodes, a high frequency voltage is applied between opposite electrodes disposed one above the other to generate plasma between the electrodes to perform plasma processing (etching and film formation) on a subject substrate placed between the electrodes. In a plasma processing apparatus provided with parallel flat electrodes, generally a wafer is placed on the lower electrode, and a reactive gas or an inactive gas is discharged through gas emission holes provided in the upper electrode. In other words, the electrode of a plasma processing apparatus serves also as a shower head for discharging gas and is provided with a plurality of gas emission holes piercing the substrate in its thickness direction.
In the parallel flat type plasma processing apparatus, at least a part of the electrode surfaces is exposed to generated plasma. In the step where the subject substrate undergoes etching, in particular, the electrode surfaces are subjected to corrosion (etching) as an active species of the reactive gas activated by plasma generated between the electrodes acts upon the electrode surfaces. When the electrode surfaces are corroded, the stability of the generated plasma decreases until finally generation of plasma becomes impossible.
Thus, the electrodes exposed to plasma in the plasma processing apparatus are consumables and there has been a demand for electrodes having a relatively high resistance to corrosion when exposed to plasma to ensure stable generation of plasma over an extended period of time and reduced running costs of the device. Thus, there have been proposed electrodes purporting to offer a relatively high resistance to corrosion when exposed to plasma, wherein at least the surface exposed to plasma is made of SiC (silicon carbide). SiC has a significantly high level of hardness and an excellent resistance to corrosion (to acid) and heat and is used not only as electric material but also as coating film material for components of semiconductors manufacturing apparatuses. SiC breaks down into sintered SiC produced by a so-called sintering method whereby pulverized SiC is sintered to obtain a relatively large structure and CVD-SiC produced by a chemical vapor deposition method.
However, SiC, when used to configure an electrode surface, considerably increases costs and time for forming through holes that serve as gas emission holes because of its mechanical strength. For example, to form through holes having a relatively small diameter of say 0.5 mm or less in a SiC material, one had no other alternative but to use a method such as ultrasonic machining that requires considerable costs and work. Thus, electrodes having a SiC surface were expensive to manufacture and also expensive to restore. Accordingly, use of SiC in the electrode surface did not aid in sufficiently reducing the running costs of the device.
The Patent Document 1 mentioned below describes an electrode for a plasma processing apparatus, wherein a porous SiC material containing numerous air holes communicating with each other and a CVD-SiC material formed with numerous through holes (gas emission holes) are stacked one on the other to form a unitary structure. The Patent Document 1 mentioned below also describes a method of manufacturing an electrode for a plasma processing apparatus, whereby, it is therein described, a CVD-SiC layer having, numerous through holes (gas emission holes) can be formed without machining the CVD-SiC material. According to the method of manufacturing an electrode for a plasma processing apparatus described in the Patent Document 1 mentioned below, a plurality of T-shaped pins each formed of a rod member and a flat plate that is joined to a part of the rod member are first disposed on one surface of a green sheet, which will be made into a porous SiC layer, with the flat plates embedded in the one surface, whereby the green sheet is allowed to undergo a sintering process to sinter it in an inert atmosphere to produce a porous SiC layer. Then, a CVD-SiC cover is formed using the CVD method on the surface of the porous SiC layer where the T-shaped pins are formed, and the surface of the CVD-SiC cover is polished to expose a part of each T-shaped pin, followed by heating in an oxidizing atmosphere for decomposition and removal of the T-shaped pins to achieve production of an electrode for a plasma processing apparatus having the above configuration.    Patent Document 1: JP 2003-59903 A